Go on google and search "Virtual Japanese Keyboard", look for the result with "branah" as the domain name. Then just match the letters on the security question to the ones on the keyboard. Click to type it out, then copy & paste it over.
Keep in mind though: There are 3 (if I remember right) different types of Japanese lettering. Hiragana, Katakana, and Kanji. (This shouldn't be a problem but if it ends up one you know why)